How likely is Mississippi River to flood this year? These areas could see moderate events
The National Weather Service St. Louis office released the latest spring flood outlook Thursday, and there’s a decent chance parts of the region will see “moderate flooding.”
Mark Fuchs, senior service hydrologist with NWS St. Louis, told the News-Democrat the probability of moderate flooding in the next 90 days is about 46% in St. Louis, and some areas have higher chances.
Grafton, Chester and Quincy are among the Illinois towns where moderate flooding is likely, and the city of Louisiana in Missouri also has a probability of moderate flooding of more than 50%.
But what exactly is moderate flooding and how common is it? Here’s what to know, with information from the NWS.
Effects of moderate flooding
Residents of areas experiencing moderate flooding may want to be cautious while driving and check road closures before traveling.
“Moderate flooding is typically the level where we start seeing major roads that are getting closed, roads that get a lot of traffic, not at your county roads but a lot of times your state roads will start flooding,” Fuchs said. “We don’t typically see a lot of structural flooding at that height, but we could certainly see roads closed.”
Public park structures like gazebos and restrooms could be flooded, along with main lines of railroad tracks, public swimming pools and state roads.
“U.S. highways could get flooded in moderate flooding,” Fuchs said.
While most of the St. Louis area is considered to have a risk of minor flooding this spring, the 46% likelihood of moderate flooding is higher than the historical average of 34%.
Fuchs said the St. Louis area near the Mississippi River generally sees moderate flooding about once every four to five years, though depending on the area, frequency could range between three to eight years. These are estimates, and the exact data varies by location.
The amount of rainfall an area receives will greatly affect the likelihood of flooding. If the region were to see heavy rains similar to 2019’s precipitation, flooding would likely be more severe, but a drier season is also possible.
“There’s a lot of probabilistic leeway involved in every spring flood outlook,” Fuchs said.
The current forecast shows the Missouri River and local tributaries are trending toward a more typical water level.
“Except for the Mississippi. Mississippi is not what we would call a normal year, this is definitely above normal,” Fuchs said.
A worst case scenario would involve snowpack from Minnesota and Wisconsin melting suddenly due to warm rains, but moderate or more severe flooding is not guaranteed in the forecast.
“We could easily not get to that moderate level, we could easily exceed it by quite a bit depending on how much rain falls from the snowpack that we have up north,” Fuchs said.
If your area does experience flooding, Fuchs recommends being aware of what water level will affect your home or business, as well as checking conditions before hitting the road.
This story was originally published March 12, 2023 at 7:00 AM.
